Packages or pouches are routinely used to contain sterilized surgical instruments such as those used in medical, dental and veterinary applications. The instruments are located inside the pouch and then sterilized using a variety of sterilants such as ethylene oxide, steam and the like. This simple approach has a number of shortcomings, one of which is the ability to monitor the sterilization conditions inside the pouch to which the instruments are exposed. A number of designs exist which are directed towards this problem. For example, in published US patent application, application number US2009/0123332A1, a package is disclosed in two indicators are located inside the pouch. The indicators are formed by ink printed on a porous paper layer. One of the indicators is located behind a barrier, which prevents contamination of the pouch contents with the ink and also allows the internal indicators to be used in the same compartment as the contents to be sterilized. However, a gap on either side of the barrier would appear to allow the ink to diffuse into the pouch, which in turn may contaminate the surgical instruments.
U.S. Pat. No. 5,344,017 which discloses a pouch having seal lines that are constructed to enclose an indicator at the tapered end of a perimetrical seal. The seal lines extend at right angles to the tapered portions of the perimetrical seal to form a diamond shaped enclosure. In this case, the indicator is located within the diamond shaped enclosure.
Disadvantageously, the major shortcomings of the above designs are that the paper layer on which the indicators are printed is porous and allows steam/ethylene oxide to penetrate the pouch from the surrounding sterilization chamber. Thus, the indicators will change colour when the sterilant comes into contact with the exterior of the pouch and therefore does not provide any added value.
Features of the discovery will be apparent from review of the disclosure, drawings and description below.